Isotope effect in the equilibrium between the silicon surface and the gas phase of hydrogen or deuterium

The equilibrium concentrations of passivating adatoms in the system of silicon crystal plus the gas of H-2 or D-2 molecules is calculated. The effect of adatom localized vibrations on the equilibrium concentrations is taken into consideration. It is shown that the major contribution to the ratio of deuterium and hydrogen surface concentrations is determined by the difference between the localized vibration frequencies of deuterium and hydrogen adatoms. The substitution of deuterium for hydrogen for passivating leads to a significant increase of the adatom concentration.